Murray, who was expected to begin his new job with the business group next month, said in an interview with The Associated Press that he had not been actively pursuing a new job after announcing earlier in the year that he did not intend to run for governor in 2014.

The lieutenant governor also said his departure had nothing to do with an ongoing investigation into whether his political committee improperly accepted campaign contributions raised by former Chelsea Housing Authority Director Michael McLaughlin.

"I wasn't seeking the position. This is something that came to me," Murray said.

The chamber first contacted him about the position about a month ago, Murray said, but he initially was not interested because he intended to complete his second term, which ends in January 2015.

He said he later decided, however, that the opportunity would be a good one professionally and for his family, and realized the job would not still be available after he leaves office.

Murray, 44, is the father of two girls, ages 7 and 8. He said he would earn more than $200,000 in the new job, though he declined to give the exact salary. He earns nearly $125,000 as lieutenant governor.

There is no provision in Massachusetts law for filling a vacancy in the lieutenant governor's office, so the position will remain vacant until after the next state election.

Secretary of State William Galvin would become the next in line to the governor's office following Murray's departure, and will serve as the state's acting governor when Patrick is traveling.

Murray, a former Worcester mayor, has enjoyed strong support from Patrick and has been credited with leading many of the administration's economic development initiatives, as well as strengthening ties with municipal officials around the state. But his tenure has also included some controversies.

In January, the state Office of Campaign and Political Finance made public a letter it sent in September to Attorney General Martha Coakley saying there was evidence Murray and his political committee broke the law by accepting donations raised by former Chelsea Housing Authority Director Michael McLaughlin.

McLaughlin pleaded guilty in February to federal charges that he knowingly concealed his salary in annual housing authority budgets from 2008 to 2011 and submitting the false figures to state and federal regulators. He admitted to falsely reporting his annual salary as $160,415 in 2011, when his total compensation was at least $324,896.

Murray has acknowledged that McLaughlin was a political supporter but that he never asked McLaughlin to raise campaign money for him, and was unaware of the allegedly bloated salary.

"Michael McLaughlin misled a whole lot of people and organization, including me," Murray said Wednesday, adding that it played no role in his decision to resign before the end of his term.

Murray also faced questions about a pre-dawn crash on Interstate 190 in November 2011 that totaled the state car he was driving. Data later released from the vehicle's "black box" show the car was traveling more than 100 miles per hour in the moments before it left the highway, hit a rock ledge and rolled over.

Murray, who was not seriously injured, was issued a $555 ticket.

His version of the events of that morning shifted during the course of the investigation. He initially told reporters he was driving around the speed limit and believed the cause of the accident was black ice, but he later said he probably fell asleep at the wheel just before the accident.

Rep. Bradley Jones, the Republican leader in the Massachusetts House, said he wished Murray well but that his resignation leaves "unanswered questions."

After entering into employment discussions with the chamber, Murray said he hired a private attorney and as a precaution, filed a notice with the state Ethics Commission because of a "potential appearance of a conflict of interest."

But Murray added that the chamber receives no state funding and had no active issues pending before the governor's office or the Legislature.

Among the lieutenant governor's responsibilities is leading the weekly meetings of the Governor's Council, an elected body that confirms judicial appointments and has been known for occasionally raucous discussions.

Patrick will likely be required to lead the council in Murray's absence.

"His Wednesdays are going to have a little more flavor," Murray joked.

Lawyers for Boston Marathon bomber Dzkokhar Tsarnaev rested their case in his federal death penalty trial Tuesday after presenting a brief case aimed at showing his late older brother was the mastermind of the 2013 terror attack.